Signs of Poor Sub-Grade

Warning Signs of Poor Sub-Grade


Construction, large and small, requires a stable foundation. The soil or rock holding up the foundation, exposed during foundation excavation, is called “sub-grade.” A quick sub-grade evaluation prior to reinforcing steel installation can identify potential pit falls and prevent a world of hurt moving forward.


Why Evaluate Sub-Grade?

A sub-grade evaluation will identify potential pitfalls, such as problem soils not observed in soil borings, or groundwater conditions that change over time.

Sub-grade evaluation prior to footing construction is typically recommended in a professional geotechnical evaluation, or Soils Report; however, the responsibility to order this service can be overlooked due to miscommunication or a variety of other reasons. If a foundation is built on a poor sub-grade, the potential exists to have excessive settlement in floors or walls.


Watch Out for Warning Signs

Warning signs of poor sub-grade soils include:

  • Changes in soil type across the excavation, like transitions from granular to cohesive soils;
  • Fill materials containing debris;
  • Old foundations, tanks, or drain tile;
  • Organic soils such as topsoil, peat/muck, and lake marl;
  • Loose sand, or even “quick” sands (due to partial dewatering); or
  • Groundwater intrusion, making compaction “in the dry” difficult.


Problem Soils? Contact Us.

If you observe any of these warning signs, call us to discuss what should be done to remedy the situation. Better yet, let us perform a sub-grade evaluation. 

Let us be your go-to for your technical construction support needs: geotechnical engineering, ground penetrating radar, vibration and crack monitoring, movement monitoring, construction staking, inspection, and materials testing. 


Reminder! Cold weather is upon us. Remember to read the Cold Weather and Frosty Soils newsletter.


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